Differences from singledispatch

While variants and singledispatch are both intended to provide alternative implementations to a primary function, the overall aims are slightly different. singledispatch transparently dispatches to variant functions based on the type of the argument, whereas variants provides explicit alternative forms of the function. Note that in the above example, both print_text.from_filepath and print_text.from_url take a string, one representing a file path and one representing a URL.

Additionally, the variants is compatible with singledispatch, so you can have the best of both worlds; an example that uses both:

@variants.primary
@singledispatch
def add(x, y):
    return x + y

@add.variant('from_list')
@add.register(list)
def add(x, y):
    return x + [y]

Which then automatically dispatches between named variants based on type:

>>> add(1, 2)
3
>>> add([1], 2)
[1, 2]

But also exposes the explicit variant functions:

>>> add.from_list([1], 2)
[1, 2]
>>> add.from_list()
      7 @add.register(list)
      8 def add(x, y):
----> 9     return x + [y]

TypeError: unsupported operand type(s) for +: 'int' and 'list'

It is important to note that the variants decorators must be the outer decorators.

Installation

To install variants, run this command in your terminal:

$ pip install variants

Requirements

This is a library for Python, with support for versions 2.7 and 3.4+.

Features

• Added the variants.inspect module, which provides a public API for inspecting variant function groups. It currently provides two functions: is_primary and is_primary_method. (GH #29)

• Added python_requires to setup, indicating Python version support. (GH #34)

Bugfixes

• Updated MANIFEST.in to include NEWS.rst (GH #34)

Improved Documentation

• Updated permanent redirect links in documentation. (GH #28)

• Flattened TOC entry for changelog in documentation. (GH #32)

• Added section for API documentation, including documentation for the inspect submodule. (GH #33)